基于电网络模型的动脉树输入阻抗递归计算及参数分析

目的 通过提出一种计算人体动脉树输入阻抗的递归算法,分析动脉树各参数对输入阻抗的影响,为动脉树生理和病理变化分析提供参考。方法 利用由大动脉和主要外周动脉构成的55段人体动脉树建立分布式电网络模型,通过设定电网络模型外周阻力,建立动脉树单向数据链表,采用递归算法计算动脉树升主动脉的输入阻抗。在此基础上比较不同动脉顺应性、外周阻力和动脉长度、内径、壁厚等参数对输入阻抗的影响。结果 计算结果与实验数据和其他模型结果相一致,验证了该方法的有效性。不同参数对动脉树输入阻抗的影响有较大差异且呈现各自特征。结论 输入阻抗能有效地反映动脉树血液动力学参数的变化情况,是人体动脉树生理病理诊断的重要参考。     

全分支的体循环混合参数计算机模拟研究

本文提出了一种改进的人体血液动脉系统的计算机模拟方法，即把动脉血流脉搏波传播的非线性（或线性）分布参数模型与线性集中参数流体网络模型混合，构造动脉系统的分布─集中混合参数模型。对模型中分布参数部分，采用非标准Ｇａｌｅｒｋｉｎ半离散空间有限元方法进行处理．通过具体建立人体体动脉系统的这种混合参数模型、并进行计算机模拟研究，结果表明，这种模拟方法既可以从系统的量级上模拟动脉系统的血流动力学特性，又可以对所感兴趣的局部血管处进行较细致的模拟，并且可以研究系统各部分间的相互影响。     

Characterization and distribution of collagen types in arterial heterografts originating from the calf carotis

Summary The immunohistochemical results showed that the distribution of the collagen types in calf carotis is the same as that found in human arteries. Mechanically prepared and ficin-treated vessels showed a removal of cells, elastic fibres and type III collagen. The remaining collagen meshwork was shown by immunohistochemical methods and also by amino acid analysis to be type I collagen. Because of its structural, chemical and immunological properties, the protease treated, aldehyde stabilised Arteria carotis communis of the calf is suitable as a replacement material for arterial segments. Initial successes using man as a recipient support the stated conclusion.Herrn Prof. Dr. Seiferle, Zürich, zum 75. Geburtstag gewidmet     

Mechanical and dimensional adaptation of rabbit carotid artery culturedin vitro

The effects of the mechanical environment on arterial walls were investigated in rabbit common carotid arteries, cultured for six days under three different intraluminal pressures (0, 80 and 160 mmHg) in a perfusion culture system. The mechanical responses following the culture were examined using a quasi-static pressure-diameter test. Specimen viability was determined by smooth muscle contraction induced with KCl. Eighteen out of 21 cultured segments showed a peak reduction in diameter of more than 10% and were used for the analysis. The arterial segments cultured at 0 mmHg had a significantly smaller diameter than those cultured at other pressures. The segments cultured at higher pressure had lower incremental elastic moduli at 20 and 80 mmHg and higher moduli at 160 mmHg. The walls of the cultured segments were thicker in groups with higher pressure. These results indicate that, even in culture, the mechanical environment is a major determinant for the mechanical property and dimensions of the arterial wall. Arterial walls may respond to their mechanical environment even if other factors, such as hormonal environment and nervous stimuli, are kept unchanged.     

Mechanical and dimensional adaptation of rabbit carotid artery culturedin vitro

The effects of the mechanical environment on arterial walls were investigated in rabbit common carotid arteries, cultured for six days under three different intraluminal pressures (0, 80 and 160 mmHg) in a perfusion culture system. The mechanical responses following the culture were examined using a quasi-static pressure-diameter test. Specimen viability was determined by smooth muscle contraction induced with KCl. Eighteen out of 21 cultured segments showed a peak reduction in diameter of more than 10% and were used for the analysis. The arterial segments cultured at 0 mmHg had a significantly smaller diameter than those cultured at other pressures. The segments cultured at higher pressure had lower incremental elastic moduli at 20 and 80 mmHg and higher moduli at 160 mmHg. The walls of the cultured segments were thicker in groups with higher pressure. These results indicate that, even in culture, the mechanical environment is a major determinant for the mechanical property and dimensions of the arterial wall. Arterial walls may respond to their mechanical environment even if other factors, such as hormonal environment and nervous stimuli, are kept unchanged.     

Validity of the transfer function model of the human arterial system of the lower limb in man

A transfer function model of the human arterial system has been examined and tested on a group of 21 patients undergoing reconstructive arterial surgery in the leg. It was found that use of the model to estimate parameters relating to proximal (above femoral artery) arterial wall stiffness and radius is not reliable, the model being affected by the peripheral resistance. The value of the model parameters relating to the peripheral arterial radius is more consistent with the theory although there are still contradictions. It is concluded that the application of transfer function modelling to the diagnosis of arterial disease should be approached with caution.     

Measuring arterial strain induced by endovascular stents

Endovascular stents are expandable, fenestrated tubes that are threaded in their collapsed state through an artery to a site of occlusion, plastically enlarged and left as permanent implants to scaffold the artery open. The stent induces large-scale vascular strains that are difficult to measure in vivo and yet can be critical determinants of stent-vessel biology. A method is developed to measure the strain tensor developed on the surface of an artery as a stent is expanded in vivo. Arterial sections are marked with reference points and imaged as the stent is expanded. An axially symmetric parametric model of the artery is determined for each expansion time-point, and these reference points are back-projected onto this surface. The back-projected reference points are grouped and analysed to determine the circumferential, axial and torsional strain tensor components in each arterial subsection. The method is characterised in vitro using bovine artery segments and a latex phantom, and is then tested on rabbits to demonstrate its feasibility in vivo. In vitro experiments on stented bovine arteries show typical post-stenting strains of 0.60, -0.26, and 0.08 mm mm-1 in the circumferential, axial and torsional directions, respectively, sampled every 1 mm along the length of the stented region. Phantom experiments characterise the RMS error of system measurements as 0.1 mm mm-1. The system is shown capable of measuring strains of straight, accessible vessels in the presence of respiratory/cardiac motion and visual glare in vivo.     

数字化大鼠动脉血管系统三维模型的建立

采用含造影剂及显色剂的填充剂对成年SD大鼠动脉血管系统进行灌注,并借助数字X射线成像设备对灌注效果进行实时监测,通过断层解剖成像系统获取切削间距为100 μm的二维断面解剖数据集(图像分辨率为4917×3446×24 bit,共1 464张),最后利用Visual C 结合可视化工具包编程实现数据集的动脉分割及三维可视化,得到数字化SD大鼠动脉血管系统的三维模型.该模型能提供大鼠动脉血管系统的空间结构信息,为实验大鼠血管系统的研究提供了更为准确可靠的形态学参考.     

四肢主干动脉损伤的治疗分析

目的：探讨四肢主干动脉损伤的有效治疗方法。方法：回顾性分析2007年1月～2012年1月47例四肢主干动脉损伤患者的治疗临床资料。外科手术42例,其中单纯动脉破裂修补术11例,直接吻合11例,大隐静脉移植术17例,人工血管移植术3例;另外5例行腔内治疗,其中覆膜支架植入3例,裸支架植入2例。结果：44例肢体成活,截肢3例。40例患者获门诊随访,为35例手术患者和5例腔内治疗病例,截肢患者均未随访。随访时间为3个月一3a,平均随访时间15个月。在接受随访的35例手术患者中有5例吻合口处血管轻度狭窄,3例移植血管内重度狭窄,l例移植血管内闭塞;腔内治疗5例无明显异常发现。结论：外科手术及腔内治疗是四肢主干动脉损伤的有效治疗方法;选择合适的治疗方法,早期诊断和治疗,是保全肢体的关键。     

Noninvasive measurement of beat-to-beat vascular viscoelastic properties in human fingers and forearms

Static and dynamic (beat-to-beat) arterial viscoelastic properties were measured noninvasively in human fingers and forearms. The volume change and pressure change were detected simultaneously by admittance plethysmography and by sphygmomanometry using the vascular unloading technique in the index and middle finger, or vice versa. These simultaneous measurements were also made on the forearms of one side and the fingers of the other side. The arterial viscoelastic properties in these segments could be successfully determined at different transmural pressure levels from 0 mm Hg to around the mean arterial pressure.     

Measuring arterial strain induced by endovascular stents

Endovascular stents are expandable, fenestrated tubes that are threaded in their collapsed state through an artery to a site of occlusion, plastically enlarged and left as permanent implants to scaffold the artery open. The stent induces largescale vascular strains that are difficult to measure in vivo and yet can be critical determinants of stent-vessel biology. A method is developed to measure the strain tensor developed on the surface of an artery as a stent is expanded in vivo. Arterial sections are marked with reference points and imaged as the stent is expanded. An axially symmetric parametric model of the artery is determined for each expansion timepoint, and these reference points are backprojected onto this surface. The backprojected reference points are grouped and analysed to determine the circum-ferential, axial and torsional strain tensor components in each arterial subsection. The method is characterised in vitro using bovine artery segments and a latex phantom, and is then tested on rabbits to demonstrate its feasibility in vivo. In vitro experiments on stented bovine arteries show typical post-stenting strains of 0.60, −0.26, and 0.08 mm mm⁻¹ in the circumferential, axial and torsional directions, respectively, sampled every 1 mm along the length of the stented region. Phantom experiments characterise the RMS error of system measurements as 0.1 mm mm⁻¹. The system is shown capable of measuring strains of straight, accessible vessels in the presence of respiratory/cardiac motion and visual glare in vivo.     

Metabolic control of large-bore arterial resistance vessels,arterioles, and veins in cat skeletal muscle during exercise

The metabolic control of the vascular bed in cat gastrocnemius muscle during exercise was studied with a new technique (Björnberg et al. 1988) permitting continuous and simultaneous recordings of arteriolar and capillary pressures, and of resistances in the following consecutive vascular section: proximal arterial resistance vessels > 25 μm, arterioles < 25 μm, and on the venous side. The study thereby provided quantitative data for resistance and active intrinsic tone in these vascular segments at rest, during graded exercise vasodilatation, and in the post-exercise period. Slight activation of the metabolic control system by low-frequency somatomotor nerve stimulation (light exercise') caused inhibition of intrinsic tone and decreased vascular resistance selectively in the arteriolar section. At increasing workloads, arteriolar resistance was further decreased, but resistance and tone in the proximal arterial resistance vessels and the veins then became clearly reduced as well. This difference in effectiveness of the metabolic control system on the different segments of the vascular bed was expressed quantitatively in terms of a ‘metabolic vasodilator index’. Graded activation of the metabolic control system led to a marked segmental redistribution of intrinsic vascular tone, in turn resulting in an increased pressure drop across the proximal arterial vessels and the veins and a decreased pressure drop over the arterioles. The observed decrease in the pre- to post-capillary resistance ratio caused, at a constant arterial pressure of 100 mmHg, a graded increase in capillary pressure with increasing workloads, at maximum vasodilatation by an average value of 14 mmHg above the resting control value of 15.4 ± 0.6 mmHg. In the post-exercise period, recovery of vascular tone to control was more rapid in the proximal arterial resistance vessels and the veins than in the arteriolar segment.     

异常体动脉供血正常左肺下叶的CT表现与解剖基础

目的探讨异常体动脉供血正常左肺下叶的CT表现及其解剖学基础。方法回顾性分析6例异常体动脉供血正常左肺下叶的CT表现及解剖。结果增强CT及术后大体标本均显示6例（100%）粗大异常动脉起源于降主动脉左侧,异常动脉直径约为12 mm,6例（100%）左下肺动脉在背段动脉起始远侧缺如。6例（100%）CT表现左肺下叶基底段呈毛玻璃影伴体积缩小,其大体标本切面见多个扩张血管,镜下肺组织部分区域见大小不等厚壁血管,肺泡腔内有多量含铁血黄素,间质内见血管扩张、充血及灶性出血。结论异常体动脉供血正常左肺下叶的CT表现可反映其解剖基础,CT增强扫描可确诊该病。     

Use of Input Impedance to Determine Changes in the Resistance of Arterial Vessels at Different Levels in Feline Femoral Bed

In many studies, the functional state of vessels of different caliber was determined by fitting the lumped parameters of a mathematical model of the bed in order to fit the vascular input impedance (Z _in) data. However, reliability of the results obtained in such a way remains uncertain. In this study, we employed a mathematical model with seven lumped parameters and Z _in experimental data to analyze the distribution of resistance across the arterial bed of the hind limb in anesthetized cats, to test reliability of this distribution and to describe the process of ascending arterial dilation followed occlusion of iliac artery. The vascular bed was divided into three segments: large arteries, medium-sized arterial vessels and precapillary resistance vessels together with venous part of the bed. Based on the data of Z _in measured in a wide frequency range (from 0 to 150 Hz) we showed that pharmacologically induced constriction and dilation of the arterial microvessels were reflected in the model by the changes in the resistance of distal precapillary vessels only, whereas the local constriction or dilation of femoral and iliac arteries as well as artificial stenosis of the femoral artery resulted exclusively in the changes of the resistance describing the state of large arteries. Using the input impedance method we could demonstrate and quantitatively describe the process of ascending arterial dilation during the post-occlusion (reactive) hyperemia. All these results prove that the model of vascular bed with seven lumped elements used in combination with input hydraulic impedance data can be an effective tool permitted to quantitatively analyze the functional state of arterial vessels of different caliber and to describe the changes in resistance of arterial vessels during vascular reactions.     

Mathematical model of an arterial stenosis,allowing for tethering

Closed-form solutions are presented for approximate equations governing the pulsatile flow of blood through models of mild axisymmetric arterial stenosis, taking into account the effect of arterial distensibility. Results indicate the existence of back-flow regions and the phenomenon of flow-reversal in the cross-sections. The effects of pulsatility of flow and elasticity of vessel wall for arterial blood flow through stenosed vessels are determined.     

Postnatal development of the vascular pattern in the rat telencephalic pia-arachnoid

Summary The postnatal changes in arrangement of the vascular system of the pia-arachnoid of rats are described based on scanning electron microscopy of microcorrosion casts and transmission electron microscopy. At birth, the distal arteries and veins are embedded in a dense plexiform network of immature capillaries. Arteries and veins are interconnected by many small capillary anastomoses. The trunks are located above the pial plexus. The underlying plexiform vessels provide the matrix for the formation of additional collateral and precortical segments during further development. During the first postnatal week, the distal pial arteries and veins become visible as separate channels and emerge from the subjacent capillary plexus. The pattern of anastomosing arterial rings is now clearly visible. The pial arterial tree can be subdivided into conductive, collateral, and precortical distributive segments, according to Jokelainen et al. (1982). Subsequently, passive expansion of the vascular system takes place during the period of rapid brain growth. In young adults the majority of the formerly closed arterial rings are interrupted, possibly by regression of single collateral arterial segments (Fig. 6). The dense venous capillary plexus of the pia is maintained during the first eight days in spite of marked brain growth. The process of reduction of this capillary plexus starts at the arterial side and proceeds from proximal to distal segments of the veins during the second and third week. The capillary segments, which provide anastomosis between arterial and venous vessels, disappear at the same time as the regression of the dense venous capillary network. Two processes may biodify the architecture of the pial vasculature during development: brain growth and maturation on the one side and cytodifferentiation of vascular walls on other.This work was presented in part at the Third World Congress for Microcirculation, Oxford, 9–14 September 1984, and was published in abstract form (1984, Int J Microcircul Clin Exp 3:308)     

The arterial supply to the brain of the yak (Bos grunniens)

Fifteen head specimens of the yak were dissected to study the arterial supply to the brain. The supply comes from the internal carotid, maxillary, occipital and vertebral arteries. Except for the internal carotid artery, the branches of the above-mentioned arteries contributed in the formation of the rete mirable of which the vascular diameter was larger and the wall was thinner. The brain was mainly supplied by branches from the internal carotid and vertebral arteries in which the blood is oxygenated. These branches joined to form the circle of Willis (Circulus arterious cerebri) in the region of the pituitary gland. The arterial supply to the cerebrum was mainly provided by the middle and rostral cerebral arteries, which arose from the internal carotid. The basilar, cerebellar and caudal cerebral arteries came from the vertebral artery. However, the adult yaks do not have the rostral communicating artery. The outer diameter at the origin of the vessels ranged from 0.40 to 2.60 mm. The outer diameter of the left arterial vessel at its origin was larger than the same vessel of the right by about 0.20 mm in the all samples.     

Fast Estimation of Arterial Vascular Parameters for Transient and Steady Beats with Application to Hemodynamic State under Variant Gravitational Conditions

Numerous parameter estimation techniques exist for characterizing the arterial system using electrical circuit analogs. These techniques are often limited by requiring steady-state beat conditions and can be computationally expensive. Therefore, a new method was developed to estimate arterial parameters during steady and transient beat conditions. A four-element electrical analog circuit was used to model the arterial system. The input impedance equations for this model were derived and reduced to their real and imaginary components. Next, the physiological input impedance was calculated by computing fast Fourier transforms of physiological aortic pressure (AoP) and aortic flow. The approach was to reduce the error between the calculated model impedance and the physiological arterial impedance using a Jacobian matrix technique which iteratively adjusted arterial parameter values. This technique also included algorithms for estimating physiological arterial parameters for nonsteady physiological AoP beats. The method was insensitive to initial parameter estimates and to small errors in the physiological impedance coefficients. When the estimation technique was applied to in vivo data containing steady and transient beats it reliably estimated Windkessel arterial parameters under a wide range of physiological conditions. Further, this method appears to be more computationally efficient compared to time-domain approaches. © 1999 Biomedical Engineering Society. PAC99: 8719Uv, 8710+e, 0230Qy     

Biomechanical Characterization of Internal Layer Subfailure in Blunt Arterial Injury

Blunt carotid artery injuries occur in 0.3% of blunt injured patients and may lead to devastating neurological consequences. However, arterial mechanics leading to internal layer subfailure have not been quantified. Twenty-two human carotid artery segments and 18 porcine thoracic aorta segments were opened to expose the intimal side and longitudinally distracted to failure. Porcine aortas were a geometrically accurate model of human carotid arteries. Internal layer subfailures were identified using videography and correlated with mechanical data. Ninety-three percent (93%) of vessels demonstrated subfailure prior to catastrophic failure. All subfailures occurred on the intimal surface. Initial subfailure occurred at 79% of the stress and 85% of the strain to catastrophic failure in younger porcine specimens, compared to 44% and 60%, respectively, in older human specimens. In most cases, multiple subfailures occurred prior to catastrophic failure. Due to limitations in human specimen quality (age, prior storage), young and fresh porcine aorta specimens are likely a more accurate model of clinical blunt carotid artery injuries. Present results indicate that vessels are acutely capable of maintaining physiologic function following initial subfailure. Delayed symptomatology commonly associated with blunt arterial injuries is explained by this mechanics-based and experimentally quantified onset of subcatastrophic failure.